How to query Code First entities based on rowversion/timestamp value?

Question

I\'ve run into a case where something that worked fairly well with LINQ to SQL seems to be very obtuse (or maybe impossible) with the Entity Framework. Specifically, I\'ve g

Answer 1

I extended jnm2’s answer to hide the ugly expression code in a extension method

Usage:

ctx.Foos.WhereVersionGreaterThan(r => r.RowVersion, myVersion);

Extension Method:

public static class RowVersionEfExtensions
{


    private static readonly MethodInfo BinaryGreaterThanMethodInfo = typeof(RowVersionEfExtensions).GetMethod(nameof(BinaryGreaterThanMethod), BindingFlags.Static | BindingFlags.NonPublic);
    private static bool BinaryGreaterThanMethod(byte[] left, byte[] right)
    {
        throw new NotImplementedException();
    }

    private static readonly MethodInfo BinaryLessThanMethodInfo = typeof(RowVersionEfExtensions).GetMethod(nameof(BinaryLessThanMethod), BindingFlags.Static | BindingFlags.NonPublic);
    private static bool BinaryLessThanMethod(byte[] left, byte[] right)
    {
        throw new NotImplementedException();
    }

    /// 

    /// Filter the query to return only rows where the RowVersion is greater than the version specified
    /// 
    /// The query to filter
    /// Specifies the property of the row that contains the RowVersion
    /// The row version to compare against
    /// Rows where the RowVersion is greater than the version specified
    public static IQueryable WhereVersionGreaterThan(this IQueryable query, Expression> propertySelector, byte[] version)
    {
        var memberExpression = propertySelector.Body as MemberExpression;
        if (memberExpression == null) { throw new ArgumentException("Expression should be of form r=>r.RowVersion"); }
        var propName = memberExpression.Member.Name;

        var fooParam = Expression.Parameter(typeof(T));
        var recent = query.Where(Expression.Lambda>(
            Expression.GreaterThan(
                Expression.Property(fooParam, propName),
                Expression.Constant(version),
                false,
                BinaryGreaterThanMethodInfo),
            fooParam));
        return recent;
    }


    /// 

    /// Filter the query to return only rows where the RowVersion is less than the version specified
    /// 
    /// The query to filter
    /// Specifies the property of the row that contains the RowVersion
    /// The row version to compare against
    /// Rows where the RowVersion is less than the version specified
    public static IQueryable WhereVersionLessThan(this IQueryable query, Expression> propertySelector, byte[] version)
    {
        var memberExpression = propertySelector.Body as MemberExpression;
        if (memberExpression == null) { throw new ArgumentException("Expression should be of form r=>r.RowVersion"); }
        var propName = memberExpression.Member.Name;

        var fooParam = Expression.Parameter(typeof(T));
        var recent = query.Where(Expression.Lambda>(
            Expression.LessThan(
                Expression.Property(fooParam, propName),
                Expression.Constant(version),
                false,
                BinaryLessThanMethodInfo),
            fooParam));
        return recent;
    }



}